title: Frozen-thawed blastocyst transfer reduces ectopic pregnancy risk: an analysis of single embryo transfer cycles in Japan.
abstract: OBJECTIVE
  To evaluate the effect of frozen-thawed blastocyst transfer on ectopic pregnancy (EP) rate.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Japanese registry of assisted reproductive medicine.
  
  
  METHODS
  Women who were registered during 2008.
  
  
  METHODS
  None.
  
  
  METHODS
  Rates of live birth, EP, and spontaneous abortion in single blastocyst and cleavage-stage ET cycles in both fresh and frozen-thawed were determined.
  
  
  RESULTS
  In the frozen-thawed single blastocyst transfer cycles, 84 EPs of 10,312 clinical pregnancies (0.81%) were reported. There were 25 EPs of 1,361 clinical pregnancies (1.8%) in fresh IVF single blastocyst transfer cycles and 19 of 1,352 (1.4%) in fresh intracytoplasmic sperm injection single blastocyst transfer cycles. The rate of EPs after frozen-thawed single blastocyst transfers varied between 0.56% and 0.97% after stratification by age group.
  
  
  CONCLUSIONS
  Frozen-thawed blastocyst transfers have reduced EP rates significantly compared with fresh blastocyst transfers.
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Saitama Medical University, Saitama, Japan. osamishr@saitama-med.ac.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishihara
authors.forename: Akira
authors.initials: A
authors.lastname: Kuwahara
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Saitoh
mesh_terms: D000328:Adult; D000465:Algorithms; D015536:Down-Regulation; D004624:Embryo Transfer / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods / Q000706:statistics & numerical data; D005615:Freezing; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008597:Menstrual Cycle / Q000502:physiology; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000453:epidemiology / Q000209:etiology*; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D056826:Single Embryo Transfer / Q000379:methods / Q000706:statistics & numerical data